From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6B2361A9F83; Tue, 30 Jun 2026 01:00:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782781243; cv=none; b=uRZi5d0AMn/YDiDnwVq4VuVoScFX1GdMPx6IeUeuduIbdlWcUL/Qlad65svzWnKKCY4+CnthlutF/QIHOJ/7N9QsQAhS6WHpj3Z2TomHp4REqsOYBVwq9qzE8JqvAaf2xCoC+ay3sGN9NGVOSbJdDX+TPw5stobDTsoT398HJUw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782781243; c=relaxed/simple; bh=+0O19YP8kgTfN+PQbqrbvnh2QbxJ1jw2D9kPd11HFR0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=CgTE7Mw4hdLC24intd1qRcRQ1z3r+s1Dui51XdKpzpdjujxhasoX2/T0DseT3jt4KQxOx/0UE2en7KHCKjzsP9owQ7xqjepxibGIfgS/c8wCHCCJsvnZ+iv0aFWwIG/POaal0F4zCYyEgC4d2NolR/DDbYAQLwXU14QSlOw0Y8Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=CMjCj8vm; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="CMjCj8vm" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CC49D1F000E9; Tue, 30 Jun 2026 01:00:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782781242; bh=scNnJr0jcGc+I8Ey89cgibghmaTHBbkbZ3uJtZ4Ysls=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=CMjCj8vmTGMiEd6DlOjN+Y2aaH5NimELhZqNChgYdwJgOvY4OgK/i2XMjYRetaipF KmaJxhyyoZkkwBFBkYY0ymUjP6vUhPz5qEswXUI60vZzOMWPrzejeHotR5Sdi2NSm/ d7rmm5r8VhuBAjnXlfani90BT28mhqSDRRV6r7Y2puL53IYxDLo0fJ8iRzErtg4NCq XyT+0pONtW8Iww5Gph6rKCE/+/QFk8xb12BhA9ITQcy55IUxTUlNkoMYYn0AYeclgb 27T2nK7TDHwrVjC1ORiWKmOWGESYOyKeHiM3nE3Yc/6pRMIJand7SRPhG5nFcuCYw/ xxFQ2FJ8uBIxg== From: SJ Park To: IgorpetinDev Cc: SJ Park , akpm@linux-foundation.org, damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/damon/vaddr: remove redundant RCU lock Date: Mon, 29 Jun 2026 18:00:32 -0700 Message-ID: <20260630010032.141941-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260629165349.4260-1-igorpetindev@gmail.com> References: Precedence: bulk X-Mailing-List: damon@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Mon, 29 Jun 2026 19:53:49 +0300 IgorpetinDev wrote: > __damon_va_three_regions() is called only by damon_va_three_regions(), > which already holds mmap_read_lock(). Since mmap_read_lock() is held, > the maple tree and VMA list are protected from concurrent changes. > Remove the unnecessary rcu_read_lock() and rcu_read_unlock() calls. > > Signed-off-by: IgorpetinDev We prefer using a real name. I show you used 'Igor Putko' as your name before. Any reason to change the name? > --- > mm/damon/vaddr.c | 2 -- > 1 file changed, 2 deletions(-) > > diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c > index d27147603..345b89b5d 100644 > --- a/mm/damon/vaddr.c > +++ b/mm/damon/vaddr.c > @@ -84,7 +84,6 @@ static int __damon_va_three_regions(struct mm_struct *mm, > * If this is too slow, it can be optimised to examine the maple > * tree gaps. > */ > - rcu_read_lock(); > for_each_vma(vmi, vma) { > unsigned long gap; > > @@ -105,7 +104,6 @@ static int __damon_va_three_regions(struct mm_struct *mm, > next: > prev = vma; > } > - rcu_read_unlock(); As Sashiko also commented, this may cause lockdep warning. Actually this was added to fix it. Refer to the previous discussions [1] for more details. How about moving rcu_read_[un]lock() to the caller test code? [1] https://lore.kernel.org/20240904004534.1189-1-sj@kernel.org Thanks, SJ [...]